Input or output devices having a roller thereon are becoming increasingly popular. The roller is typically arranged to enable a user to scroll a display on a screen. If the roller if depressed, an extra predetermined program or function will be activated, such as logging onto the internet, receiving e-mails, and so forth. Because of the convenience of the roller, manufacturers are rushing to create or to build related structures or methods for practical use.
U.S. Pat. No. 5,912,661, U.S. Pat. No. 6,157,369, and U.S. Pat. No. 6,326,949 show conventional encoder devices that utilize a grating wheel and in which a light transmitter and a light detector are located at each side of the grating wheel. The projected light from the transmitter is intermittently blocked by a plurality of slots on the grating wheel that causes the detector to sense the changes in dark and light as to output an intermittent electrical signal. Disadvantages of this arrangement are that the transmitter and detector must be in precise alignment, and the transmitter must emit light continuously even when the grating wheel blocks transmission, so that further movement of the grating wheel can be detected.
U.S. Pat. No. 6,198,057 shows an alternative arrangement in which a rotary encoder 2 is coupled with an axle 5 of a roller 4, and a plurality of brushes are rotatably-connected with a corresponding number of contacts to generate an intermittent signal. This arrangement is simpler to assemble than optical encoders, and only a generates and electric signal when contact is made, but still requires relatively precise alignment of contacts and encoder wheel.
Finally, U.S. Pat. No. 5,657,051 discloses a switch-like encoder arranged to output intermittent signals following depression of a user's finger. The structure is easy to build, but the way that the user has to move his finger forward and backward tends not only to cause fatigue over the user's hand, but also inconvenience in use in comparison with the roller type.